530 research outputs found
On Modeling Three-Phase Flow in Discretely Fractured Porous Rock
Numerical modeling of fluid flow and dissolved species transport in the subsurface is a challenging task, given variability and measurement uncertainty in the physical properties of the rock, the complexities of multi-fluid interaction, and limited computational resources. Nonetheless, this thesis seeks to expand our modeling capabilities in the context of contaminant hydrogeology. We describe the numerical simulator CompFlow Bio and use it to model invasion of a nonaqueous phase liquid (NAPL) contaminant through the vadose zone and below the water table in a fractured porous rock. CompFlow Bio is a three-phase, multicomponent, deterministic numerical model for fluid flow and dissolved species transport; it includes capillary pressure and equilibrium partitioning relationships. We have augmented the model to include randomly generated, axis-aligned, discrete fracture networks (DFNs). The DFN is coupled with the porous medium (PM) to form a single continuum. The domain is discretized using a finite-volume scheme in an unstructured mesh of rectilinear control volumes (CVs).
Herein we present the governing equations, unstructured mesh creation scheme, algebraic development of fracture intersection CV elimination, and coupling of PM CVs over a fracture plane to permit asperity contact bridged flow. We include: small scale two-phase water-air and NAPL-water simulations to validate the practice of intersection CV elimination; small scale simulations with water-air, NAPL-water, and NAPL-water-air systems in a grid refinement exercise and to demonstrate the effect of asperity contact bridged flow; intermediate scale 3D simulations of NAPL invading the saturated zone, based on the Smithville, Ontario, site; intermediate scale 2D and 3D simulations of NAPL invading the vadose zone and saturated zone with transient recharge, based on the Santa Susana Field Laboratory site, California.
Our findings indicate that: the formulation provides a practical and satisfactory way of modeling three-phase flow in discretely fractured porous rock; numerical error caused by spatial discretization manifests itself as several biases in physical flow processes; that asperity contact is important in establishing target water saturation conditions in the vadose zone; and simulation results are sensitive to relative permeability-saturation-capillary pressure relationships. We suggest a number of enhancements to CompFlow Bio to overcome certain computational limitations
Fluid trapping during capillary displacement in fractures
International audienceThe spatial distribution of fluid phases and the geometry of fluid-fluid interfaces resulting from immiscible displacement in fractures cast decisive influence on a range of macroscopic flow parameters. Most importantly, these are the relative permeabilities of the fluids as well as the macroscopic irreducible saturations. They also influence parameters for component (solute) transport, as it usually occurs through one of the fluid phase only. Here, we present a numerical investigation on the critical role of aperture variation and spatial correlation on fluid trapping and the morphology of fluid phase distributions in a geological fracture. We consider drainage in the capillary dominated regime. The correlation scale, that is, the scale over which the two facing fracture walls are matched, varies among the investigated geometries between L/256 and L (self-affine fields), L being the domain/fracture length. The aperture variability is quantified by the coefficient of variation (ÎŽ), ranging among the various geometries from 0.05 to 0.25. We use an invasion percolation based model which has been shown to properly reproduce displacement patterns observed in previous experiments. We present a quantitative analysis of the size distribution of trapped fluid clusters. We show that when the in-plane curvature is considered, the amount of trapped fluid mass first increases with increasing correlation scale Lc and then decreases as Lc further increases from some intermediate scale towards the domain length scale L. The in-plane curvature contributes to smoothening the invasion front and to dampening the entrapment of fluid clusters of a certain size range that depends on the combination of random aperture standard deviation and spatial correlation
Simulating the TCE DNAPL Source Zone Below the Water Table at the Santa Susanna Field Laboratory
Both 2D and 3D numerical models using the CompFlow Bio were built to simulate TCE introduced from 1940 through 1990 due to industrial activities, in the fractured bedrock with a turbidities sequence of sandstones with shale interbeds underneath the Santa Susana Field Laboratory (SSFL). The domain size is 50m x 0.3m x100m and the fracture apertures are 75 and 100 microns in the 2D conceptual model; while due to computational limits, the domain size is 5m x 5m x15m and the fracture apertures are 75 ~ 150 microns in the 3D conceptual model. The bulk hydraulic conductivity estimate from 2D simulation is on the level of 10-7 m/s, which is less than that estimate from 3D one whose values is on the level of 10-6 m/s. With the rock core VOC analyses for the source zone and outflow boundary (only for 2D domain) compared with field data from SSFL, it presents that NAPL is original dominant phase of TCE in the water, and then it tends to dissolve and so as to be finally fluxed out of the domain. And by investigating the mass flux of TCE in the aqueous phase exists the fence boundary in fracture and matrix, Flow through fracture is proved to be easier than that through matrix, and larger fractures become the main conduit
Site Investigation and Modelling of DNAPL Migration in a Fractured-Porous Media
The present work is in the area of site and computational investigations dealing with migration of a dense non-aqueous phase liquid (DNAPL) within a discrete fractures network embedded in a porous rock media at field scale using numerical simulation. The migration of DNAPL in the subsurface is dependent upon surface parameters, subsurface aquifer parameters and other subsurface conditions. Generally, these aquifer parameters govern the temporal and spatial variability of a DNAPL. To understand the source zone architecture and dissolved plume movement in the subsurface, characterization of these relevant subsurface parameters is required with respect to space and time. The present study focuses on a systematic investigation and characterization of fluid and transport parameters at highly contaminated fractured-porous media site located at Smithville, Ontario, Canada.
Data used to characterize the Smithville site include site geology, ground surface elevation, historical hydraulic head, hydraulic parameters from packer tests such as hydraulic conductivity, porosity, analyses performed on borehole core samples, pumping rates from recovery wells, and contaminants transport parameters such as DNAPL concentration data. Geostatistical and statistical analysis have been used to generate information on groundwater flow direction, vertical hydraulic gradients, contaminant plume migration and source zone architecture. TCE concentrations and pumping rates have been used to estimate TCE mass removal from the site. Important parameters for use in the multiphase model have been developed, including capillary pressure curves and relative permeability curves for rock matrix and fractures, and pore throat radius of the rock matrix.
DNAPL behaves differently in fractured-porous media than it does in porous media. To understand DNAPL behaviour in fractured-porous media, site specific conceptual model development to describe geological, hydrogeological, fracture network, and DNAPL occurrence is required. Prediction of the impact of source mass depletion at highly contaminated fractured-porous media site for achieving regulatory goals, as a contaminant concentration at a down gradient compliance boundary was evaluated using multiphase compositional model CompFlow. The results demonstrate that a large amount of non-aqueous phase DNAPL is present in the Vuggy Dolostone and the Tight Dolostone (23-28m, Low Vinemount) and a small amount is present in Permeable Dolostone (Eramosa). The peak concentration at the compliance boundary is much greater than the maximum acceptable concentration (MAC) for TCE of 0.005 mg/L for drinking water
DNAPL remediation of fractured rock evaluated via numerical simulation
Fractured rock formations represent a valuable source of groundwater and can be highly
susceptible to contamination by dense, non-aqueous phase liquids (DNAPLs). The goal
of this research is to evaluate the effectiveness of three accepted remediation technologies
for addressing DNAPL contamination in fractured rock environments.
The technologies under investigation in this study are chemical oxidation, bioremediation,
and surfactant flushing. Numerical simulations were employed to examine the
performance of each of these technologies at the field scale. The numerical model
DNAPL3D-RX, a finite difference multiphase flow-dissolution-aqueous transport code
that incorporates RT3D for multiple species reactions, was modified to simulate fractured
rock environments. A gridding routine was developed to allow the model to accurately
capture DNAPL migration in fractures and aqueous phase diffusion gradients in the
matrix while retaining overall model efficiency. Reaction kinetics code subroutines
were developed for each technology so as to ensure the key processes were accounted for
in the simulations. The three remedial approaches were systematically evaluated via
simulations in two-dimensional domains characterized by heterogeneous orthogonal
fracture networks parameterized to be representative of sandstone, granite, and shale.
Each simulation included a DNAPL release at the water table, redistribution to pools and
residual, followed by 20 years of âageingâ under ambient gradient conditions. Suites of
simulations for each technology examined a variety of operational issues including the
influence of DNAPL type and remedial fluid injection protocol. Performance metrics included changes in mass flux exiting, mass destruction in the matrix versus the fractures,
and percentage of injected remedial fluid interacting with the target contaminant.
The effectiveness of the three remediation technologies covered a wide range; the mass of
contaminants destroyed were found to range from 15% to 99.5% of the initial mass
present. Effectiveness of each technology was found to depend on a variety of critical
factors particular to each approach. For example, in-situ chemical oxidation was found
to be limited by the organic material present in the matrix of the rocks, while the
efficiency of enhanced bioremediation was found to be related to factors such as the
location of indigenous bacteria present in the domain and rate of bioremediation.
In the chemical oxidation study, the efficiency of oxidant consumption was observed to
be poor across the suite of scenarios, with greater than 90% of the injected permanganate
consumed by natural oxidant demand. This study further revealed that the same factors
that contributed to forward diffusion of contaminants prior to treatment are critical to this
remediation method as they can determine the extent of contaminant destruction during
the injection period.
Bioremediation in fractured rock was demonstrated to produce relatively good results
under robust first-order decay rates and active microorganisms throughout the fractures
and matrix. It was demonstrated that under ideal conditions, of the total initial mass
present, up to 3/4 could be reduced to ethene, indicating bioremediation may be a
promising treatment approach due to the effective penetration of electron donor into the matrix during the treatment period and the ongoing treatment that occurs after injection
ceases. However, when indigenous bacteria was assumed to exist only within the
fractured walls of sandstone, it was found that under the same conditions, the rate of
dechlorination was 200 times less than the Base Case. Since the majority of the mass
resided in the matrix, lack of bioremediation in the matrix significantly reduced the
effectiveness of treatment.
Surfactant treatment with Tween-80 was proven to be a relatively effective technique in
enhanced solubilisation of DNAPL from the fractures within the domain. However, by
comparing the aqueous and sorbed mass at the start and end of the Treatment stage, it is
revealed that surfactant treatment is not efficient in removing these masses that reside
within the matrix. Furthermore, DNAPLs identified in dead end vertical fractures were
found to remain in the domain by the end of the simulations across all scenarios studied;
indicating that the injected surfactant experiences difficulty in accessing DNAPLs
entrapped in dead end fractures.
Altogether, the results underscore the challenge of restoring fractured rock aquifers due
to the field scale limitations on sufficient contact between remedial fluids and in situ
contaminants in all but the most ideal circumstances
Modeling coupled thermohaline flow and reactive solute transport in discretely-fractured porous media
Tableau dâhonneur de la FacultĂ© des Ă©tudes supĂ©rieures et postdoctorales, 2005-2006Un modĂšle numĂ©rique tridimensionnel a Ă©tĂ© dĂ©veloppĂ© pour la simulation du systĂšme chimique quartz-eau couplĂ© avec lâĂ©coulement Ă densitĂ© et viscositĂ© variable dans les milieux poreux discrĂštement fracturĂ©s. Le nouveau modĂšle simule aussi le transfert de chaleur dans les milieux poreux fracturĂ©s en supposant que lâexpansion thermique du milieu est nĂ©gligeable. Les propriĂ©tĂ©s du fluide, densitĂ© et viscositĂ©, ainsi que les constantes chimiques (constant de taux de dissolution, constant dâĂ©quilibre, coefficient dâactivitĂ©) sont calculĂ©es en fonction de la concentration des ions majeurs et de la tempĂ©rature. Des paramĂštres de rĂ©action et dâĂ©coulement, comme la surface spĂ©cifique du minĂ©ral et la permĂ©abilitĂ© sont mis jour Ă la fin de chaque pas de temps avec des taux de rĂ©action explicitement calculĂ©s. Le modĂšle suppose que des changements de la porosite et des ouvertures de fractures nâont pas dâimpact sur lâemmagasinement spĂ©cifique. Des pas de temps adaptatifs sont utilisĂ©s pour accĂ©lĂ©rer et ralentir la simulation afin dâempĂȘcher des rĂ©sultats non physiques. Les nouveaux incrĂ©ments de temps dĂ©pendent des changements maximum de la porositĂ© et/ou de lâouverture de fracture. Des taux de rĂ©action au niveau temporel L+1 (schĂ©ma de pondĂ©ration temporelle implicite) sont utilisĂ©s pour renouveler tous les paramĂštres du modĂšle afin de garantir la stabilitĂ© numĂ©rique. Le modĂšle a Ă©tĂ© vĂ©rifiĂ© avec des problĂšmes analytiques, numĂ©riques et physiques de lâĂ©coulement Ă densitĂ© variable, transport rĂ©actif et transfert de chaleur dans les milieux poreux fracturĂ©s. La complexitĂ© de la formulation du modĂšle permet dâĂ©tudier des rĂ©actions chimiques et lâĂ©coulement Ă densitĂ© variable dâune façon plus rĂ©aliste quâauparavant possible. En premier lieu, cette Ă©tude adresse le phĂ©nomĂšne de lâĂ©coulement et du transport Ă densitĂ© variable dans les milieux poreux fracturĂ©s avec une seule fracture Ă inclinaison arbitraire. Une formulation mathĂ©matique gĂ©nĂ©rale du terme de flottabilitĂ© est dĂ©rivĂ©e qui tient compte de lâĂ©coulement et du transport Ă densitĂ© variable dans des fractures de toute orientation. Des simulations de lâĂ©coulement et du transport Ă densitĂ© variable dans une seule fracture implantĂ© dans une matrice poreuse ont Ă©tĂ© effectuĂ©es. Les simulations montrent que lâĂ©coulement Ă densitĂ© variable dans une fracture cause la convection dans la matrice poreuse et que la fracture Ă permĂ©abilitĂ© Ă©levĂ©e agit comme barriĂšre pour la convection. Le nouveau modĂšle a Ă©tĂ© appliquĂ© afin de simuler des exemples, comme le mouvement horizontal dâun panache de fluide chaud dans un milieu fracturĂ© chimiquement rĂ©actif. Le transport thermohalin (double-diffusif) influence non seulement lâĂ©coulement Ă densitĂ© variable mais aussi les rĂ©actions chimiques. LâĂ©coulement Ă convection libre dĂ©pend du contraste de densitĂ© entre le fluide (panache chaud ou de lâeau salĂ©e froide) et le fluide de rĂ©fĂ©rence. Dans lâexemple, des contrastes de densitĂ© sont gĂ©nĂ©ralement faibles et des fractures nâagissent pas comme des chemins prĂ©fĂ©rĂ©s mais contribuent Ă la dispersion transverse du panache. Des zones chaudes correspondent aux rĂ©gions de dissolution de quartz tandis que dans les zones froides, la silice mobile prĂ©cipite. La concentration de silice est inversement proportionnelle Ă la salinitĂ© dans les rĂ©gions Ă salinitĂ© Ă©levĂ©e et directement proportionnelle Ă la tempĂ©rature dans les rĂ©gions Ă salinitĂ© faible. Le systĂšme est le plus sensible aux inexactitudes de tempĂ©rature. Ceci est parce que la tempĂ©rature influence non seulement la cinĂ©tique de dissolution (Ă©quation dâArrhenius), mais aussi la solubilitĂ© de quartz.A three-dimensional numerical model is developed that couples the quartz-water chemical system with variable-density, variable-viscosity flow in fractured porous media. The new model also solves for heat transfer in fractured porous media, under the assumption of negligible thermal expansion of the rock. The fluid properties density and viscosity as well as chemistry constants (dissolution rate constant, equilibrium constant and activity coefficient) are calculated as a function of the concentrations of major ions and of temperature. Reaction and flow parameters, such as mineral surface area and permeability, are updated at the end of each time step with explicitly calculated reaction rates. The impact of porosity and aperture changes on specific storage is neglected. Adaptive time stepping is used to accelerate and slow down the simulation process in order to prevent physically unrealistic results. New time increments depend on maximum changes in matrix porosity and/or fracture aperture. Reaction rates at time level L+1 (implicit time weighting scheme) are used to renew all model parameters to ensure numerical stability. The model is verified against existing analytical, numerical and physical benchmark problems of variable-density flow, reactive solute transport and heat transfer in fractured porous media. The complexity of the model formulation allows chemical reactions and variable-density flow to be studied in a more realistic way than previously possible. The present study first addresses the phenomenon of variable-density flow and transport in fractured porous media, where a single fracture of an arbitrary incline can occur. A general mathematical formulation of the body force vector is derived, which accounts for variable-density flow and transport in fractures of any orientation. Simulations of variable-density flow and solute transport are conducted for a single fracture, embedded in a porous matrix. The simulations show that density-driven flow in the fracture causes convective flow within the porous matrix and that the highpermeability fracture acts as a barrier for convection. The new model was applied to simulate illustrative examples, such as the horizontal movement of a hot plume in a chemically reactive fractured medium. Thermohaline (double-diffusive) transport impacts both buoyancy-driven flow and chemical reactions. Free convective flow depends on the density contrast between the fluid (hot brine or cool saltwater) and the reference fluid. In the example, density contrasts are generally small and fractures do not act like preferential pathways but contribute to transverse dispersion of the plume. Hot zones correspond to areas of quartz dissolution while in cooler zones, precipitation of imported silica prevails. The silica concentration is inversely proportional to salinity in high-salinity regions and directly proportional to temperature in low-salinity regions. The system is the most sensitive to temperature inaccuracy. This is because temperature impacts both the dissolution kinetics (Arrhenius equation) and the quartz solubility
Hydro-Mechanical-Chemical Coupled Processes in Fractured Porous Media: Pressure Solution Creep
Pressure solution creep is a fundamental deformation mechanism in the upper crust. Overburden pressure that acts upon layers of sediment leaves grains densely packed. Nonhydrostatic stress distributed over the contacts between grains brings an enhancement effect on surface dissolution. As surface retreat over the contacts and hence grain repacking squeeze out pore water in the voids, the layers of sediment are deformed to become denser and denser.
This work aims to identify what process slows down pressure solution creep over time. For this purpose, a new mechanistic model of pressure solution creep is developed, derived from the reaction rate law for nonhydrostatic dissolution kinetics under the hypothesis of a closed system. The present mechanistic model shows that (1) the creep rate goes down as a combined consequence of stress transfer across expanding contacts and concentration build-up in the interlayer of absorbed water; and (2) solute migration process acts as the primary rate-limiting process of pressure solution creep in the long run.
This work then focuses on hydraulic evolution of channelling flow through a single deformable fracture which is simultaneously subjected to pressure solution creep. The developed 1-D reactive transport model is allowed to capture the strong interaction between channelling flow and pressure solution creep under crustal conditions. This numerical investigation provides a justified interpretation for the unusual experimental observation that fracture permeability reduction does not necessarily cause concentration enrichment. Temperature elevation contributes to accelerating the progression of pressure solution creep
Flow and transport in fractured geothermal reservoirs on different scales: Linking experiments and numerical models
Die ErdwÀrme stellt eine wichtige erneuerbare Energiequelle der Zukunft dar,
um den Grundbedarf der Menschen an WĂ€rme und Strom zu decken und die
AbhÀngigkeit von fossilen Brennstoffen wie Erdöl und Kohle zu verringern.
Die Internationale Energiebehörde schÀtzt, dass bis zum Jahr 2050 3,5% der
weltweiten Energieversorgung durch Geothermie erfolgen können. Die Vorteile
der Geothermie liegen dabei in der guten bedarfsabhÀngigen Regulierbarkeit
sowie der uneingeschrĂ€nkten weltweiten VerfĂŒgbarkeit bei gleichzeitig geringem
FlĂ€chenbedarf. DarĂŒber hinaus ist die Geothermie als eine der wenigen
erneuerbaren Energien vollstÀndig grundlastfÀhig und damit unabhÀngig von
stark wechselnden UmwelteinflĂŒssen, wie WindstĂ€rke oder Sonneneinstrahlung.
Die gröĂte Herausforderung bei der Geothermie liegt in der ErschlieĂung
von Niederenthalpie-LagerstÀtten, die in Tiefen von einigen Kilometern liegen.
Eine Möglichkeit hierzu stellt die Technologie des Enhanced Geothermal
Systems (EGS) dar, die geringdurchlÀssige Gesteinsschichten eines Reservoirs
wirtschaftlich nutzbar macht. Bei EGS werden durch hydraulische Stimulation
bestehende natĂŒrliche Kluftsysteme erweitert und neue KlĂŒfte geschaffen und so
ein effektiver WĂ€rmeaustausch zwischen dem geklĂŒfteten Reservoirgestein und
zirkulierenden Fluiden ermöglicht. Bisher gibt es allerdings nur wenige Pilotanlagen,
wie z.B. in Soultz-sous-ForĂȘts, Frankreich. Der Nachteil dieser Technologie
ist, dass die so entstandenen KlĂŒfte nur einen sehr kleinen Teil des Reservoirvolumens
darstellen und sich alle an der Fluidzirkulation beteiligten natĂŒrlichen
und induzierten Prozesse auf engstem Raum abspielen. Das grundlegende VerstÀndnis
der hochlokalisierten physikalischen Prozesse und Wechselwirkungen
stellt somit den SchlĂŒsselfaktor fĂŒr einen erfolgreichen, umweltvertrĂ€glichen
und sicheren Betrieb von EGS dar.
Ein besonderes Augenmerk muss auf die gegenseitigen Wechselwirkungen
zwischen der Kluft und dem zirkulierenden Fluid sowie dem damit verbundenen
Transport von WÀrme und gelösten Stoffen gelegt werden. Die Kluftöffnung
wird oft vereinfacht als der Abstand zwischen zwei parallelen Platten dargestellt.
In Wirklichkeit bestehen die Verbindungen zwischen zwei Bohrungen jedoch
aus einem kleinrĂ€umigen Netzwerk einzelner KlĂŒfte, die wiederum ein stark
verÀnderliches inneres Porenvolumen aufweisen.
Die vorliegende Arbeit trÀgt zu einem besseren VerstÀndnis der Entstehung
und geometrischen Beschaffenheit von bevorzugten Fluidwegsamkeiten in geklĂŒfteten
Reservoiren sowie der damit verbundenen Transportprozesse bei. Das
ĂŒbergeordnete Ziel der einzelnen Studien ist eine VerknĂŒpfung experimenteller
Untersuchungen mit numerischen Modellen, um die relevanten, teilweise
skalenabhĂ€ngigen physikalischen Prozesse in KlĂŒften zu identifizieren und
quantifizieren.
In den ersten beiden Studien (Kapitel 4 und 5) werden eine Vielzahl von stochastisch
einzigartigen granitĂ€hnlichen Kluftgeometrien erstellt. AnschlieĂend
werden numerische Modelle entwickelt, um die prÀferentiellen Fluidpfade und
deren Eigenschaften im Klufhohlraum unter geothermie-typischen Strömungsbedingungen
und unter Verwendung der komplexen Navier-Stokes-Gleichungen
zu quantifizieren.
Das Ziel der ersten Studie ist die Quantifizierung von rÀumlichen Unterschieden
zwischen den dreidimensionalen und den vereinfachten zweidimensionalen
Kluftmodellen. Ein Vergleich zwischen Àquivalenten Modellierungen mittels der
Navier-Stokes-Gleichungen und dem lokalen kubischen Gesetz erlaubt eine Vorhersage
ĂŒber die GĂŒltigkeit dieser Vereinfachungen. In AbhĂ€ngigkeit von FlieĂund
Scherrichtung sowie dem angelegten Druckgradienten bilden sich in allen
KlĂŒften KanĂ€le aus, die einen groĂen Teil des Volumenstroms umfassen, wĂ€hrend
im Rest der Kluft nur geringe Anteile an Fluidbewegung zu beobachten sind.
Innerhalb dieser KanĂ€le zeigen beide FlieĂgesetze eine gute Ăbereinstimmung
sowohl fĂŒr rein laminare als auch turbulente Strömungen (mit Reynolds-Zahlen
deutlich ĂŒber 1). AuĂerhalb von KanĂ€len ergibt sich unabhĂ€ngig vom FlieĂregime
fĂŒr die zweidimensionale Vereinfachung eine deutliche ĂberschĂ€tzung
des zu erwartenden Volumenstroms. In der zweiten Studie werden die einzelnen
KanÀle innerhalb der dreidimensionalen Kluft hinsichtlich ihrer Geometrie
sowie Transporteigenschaften quantifiziert. Die Ergebnisse zeigen eine starke
Anisotropie hinsichtlich der FlieĂ- und Scherrichtung. Obwohl eine senkrechte
Ausrichtung von Strömung und Scherung zu einem deutlich verbesserten
Durchfluss fĂŒhrt, haben die gut ausgebildeten und geraden KanĂ€le nur eine begrenzte
KontaktflÀche mit dem umgebenden Gestein und behindern somit einen
effizienten WĂ€rmeaustausch. Anders ist dies bei einer parallelen Ausrichtung
von Scherung und Strömung. In diesem Fall sind die KanÀle deutlich weniger
ausgeprĂ€gt und haben zudem einen stark verlĂ€ngerten absoluten FlieĂweg und
damit verbundene höhere KontaktflÀche.
Die dritte Studie (Kapitel 6) umfasst die VerknĂŒpfung von Triaxialexperimenten,
durchgefĂŒhrt an zwei Sandsteinenderivaten mit steigenden Temperaturund
Druckbedingungen, mit numerischen Modellen. Ziel ist eine Vorhersage
der hydraulischen und mechanischen Gesteinseigenschaften eines potentiellen
Reservoirgesteins. Die Ergebnisse zeigen eine poroelastische Kompaktion des
Gesteins sowie anschlieĂende nichtlineare Deformation, welche beide mit numerischen
Modellen vorhergesagt werden können. Das Drucker-Prager-Kriterium
ermöglicht die Bewertung der kritischen Scherspannung unter BerĂŒcksichtigung
der drei Hauptspannungen. Die Studie zeigt, dass kleinstskalige VerÀnderungen,
wie die mineralogische Zusammensetzung, zwar die Materialeigenschaften des
Gesteins beeinflussen, numerische und analytische Modelle dessen Verhalten
dennoch beschreiben können.
In der vierten und fĂŒnften Studie (Kapitel 7 und 8) werden die kleinskalig gewonnen
Erkenntnisse sowie weiterfĂŒhrende Felduntersuchungen dazu genutzt,
um ein Modell des groĂrĂ€umigen Strömungsregimes im geklĂŒfteten Reservoir
von Soultz-sous-ForĂȘts zu entwickeln. In der vierten Studie wird ein Strukturmodell
des Soultz-Reservoirs entwickelt und das Strömungsregime entlang
von KlĂŒften zwischen den einzelnen Bohrungen mittels numerischer Modelle
bestimmt. Durch die VerknĂŒpfung mit den experimentellen Daten mehrerer
Zirkulations- sowie Tracerversuche kann das Strömungsregime in bohrlochfernen
Bereichen des Reservoirs quantifiziert werden. DarĂŒber hinaus kann eine
geologische Struktur identifiziert werden, die die Bohrungen GPK3 und GPK4
zwar hydraulisch separiert, allerdings störungsparallel eine Anbindung an das
FlieĂregime des Oberrheingrabens herstellt. In der fĂŒnften Studie wird auf
Grundlage des zuvor entwickelten hydraulischen Modells die SensitivitÀt der
Produktionstemperatur hinsichtlich verschiedener operativer Rahmenbedingungen
(Injektionstemperatur und FlieĂraten) untersucht
Tracing back the source of contamination
From the time a contaminant is detected in an observation well, the question of where and when the contaminant was introduced in the aquifer needs an answer. Many techniques have been proposed to answer this question, but virtually all of them assume that the aquifer and its dynamics are perfectly known. This work discusses a new approach for the simultaneous identification of the contaminant source location and the spatial variability of hydraulic conductivity in an aquifer which has been validated on synthetic and laboratory experiments and which is in the process of being validated on a real aquifer
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